Serum/plasma separator - piston with red-cell trapping surfaces

ABSTRACT

A self-contained fluid separator assembly capable of separating blood into its component parts of plasma or serum, the light phase, and cellular portion, the heavy phase, is disclosed. A piston is slidably disposed in a container having its lateral outer surfaces in sealing contact with the inner surfaces of the container. Pressure responsive valve means is provided on the piston. The piston also has a throat portion leading from its lower surface to the orifices of the valve means. The walls of the throat are serrated, with a series of ridges which serve to create cavitites or pockets where the velocity of fluids flowing through the throat is reduced. A stop means is formed on the container so that the piston as it moves through the light phase will contact the stop means and stop a predetermined distance from the closure means.

[ 1 Jan. 21, 1975 SERUM/PLASMA SEPARATOR PISTON WITH RED-CELL TRAPPINGSURFACES [75] Inventor: Waldemar A. Ayres, Rutherford,

[73] Assignee: Becton, Dickinson and Company,

East Rutherford, NJ.

22 Filed: Feb. 27, 1974 211 Appl. No.: 446,391

[52] U.S. Cl 210/516, 23/359, 128/272, 210/532, 210/DIG. 23 [51] Int. ClB0ld 21/26 [58] Field of Search 23/230 B, 258.5, 259, 292; 128/214 R, 2F, 272, 218 M; 210/83, 84, 131, 359, 514-518, 532, DIG. 23, DIG. 24;

Primary Examiner-John Adee Assistant ExaminerRobert G. Mukai Attorney,Agent, or Firm-Kane, Dalsimer, Kane, Sullivan and Kurucz [57] ABSTRACT Aself-contained fluid separator assembly capable of separating blood intoits component parts of plasma or serum, the light phase, and cellularportion, the heavy phase, is disclosed. A piston is slidably disposed ina container having its lateral outer surfaces in sealing contact withthe inner surfaces of the container. Pressure responsive valve means isprovided on the piston. The piston also has a throat portion leadingfrom its lower surface to the orifices of the valve means. The walls ofthe throat are serrated, with a series of ridges which serve to createcavitites or pockets where the velocity of fluids flowing through thethroat is reduced. A stop means is formed on the container so that thepiston as it moves through the light phase will contact the stop meansand stop a predetermined distance from the closure means.

5 Claims, 2 Drawing Figures SERUM/PLASMA SEPARATOR PISTON WITH RED-CELLTRAPPING SURFACES BACKGROUND OF THE INVENTION 1. Field of the InventionThe invention concerns apparatus for the separation and isolation ofblood plasma and blood serum from whole blood.

2. Brief Description of the Prior Art It is known to separate blood intoits component parts by centrifugation, particularly employing a sealedcontainer such as is disclosed in U.S. Pat. No. 2,460,641. This patentdiscloses a container having a closure at its open end which is capableof being penetrated by a cannula through which blood passes into thecontainer. Clinical laboratories have heretofore used this device tocollect a blood sample for subsequent separation into a light phase,i.e., the serum or plasma and the heavy phase, i.e., the cellularportion. The light phase is then decanted from the cellular portion byany conventional means, for example by the use of a syringe fitted witha cannula, or a pipette, or the like.

An apparatus also heretofore employed for the separation of blood isdisclosed in US. Pat. No. 3,508,653. This patent discloses aself-contained assembly for separation of body fluid, such as blood, inwhich a deformable piston is disposed in the container and is positionedinitially adjacent the stopper for closing the container. After theblood to be separated is in the container the assembly is centrifuged.After the blood is separated, increased centrifugal force is applied tothe container, the seal between the inner surface of the container andpiston is broken and the piston is deformed, moving down through thelight phase with the light phase passing solely around the lateralsurfaces of the piston and the inner surfaces of the container. When thepiston reaches the interface between the light phase and the heavyphase, the piston movement is stopped, the force is terminated, and theseal is reestablished between the inner surface of the container and theresilient piston to present a barrier between the two phases.

Disclosed in my US. Pat. No. 3,799,383 is a serumplasma separator of thetype contemplated herein and as compared with which the presentapparatus utilizes certain different principles and differentstructures. The piston component of this prior art device is disclosedas having a valve means in association therewith through which the lightphase blood component passes during piston descent by centrifugation. Asmoothwalled throat leading to the valve means directs the flow ofliquid phase component to the valve means. In recognition of the factthat small particles of solid materials normally found in blood may becarried with liquid components through the valve means, a preferredembodiment of the apparatus disclosed in US. Pat. No. 3,779,383comprises one wherein a filter element is disposed in the throat leadingto the valve means.

The present invention, provides means increasing the likelihood oftrapping small blood clots or other undesirable material.

Other devices known to the art are generally the filtration deviceswhich separate blood into its component phases such as those disclosedin US. Pat. Nos. 3,481,477 and 3,512,940.

SUMMARY OF THE INVENTION The invention comprises: a self-contained fluidseparator assembly capable of separating blood into its component partsof plasma or serum and cellular part comprising (a) a container havingat least one open end which is adapted to receive blood for subsequentseparation into a light phase and a heavy phase; (b) a closure sealingthe open end of the container, the closure being formed of a selfsealingelastomeric material which is penetrable by a cannula through whichblood to be separated is conducted into the container; (c) a pistonhaving a specific gravity greater than the cellular portion of the bloodand slidably mounted in the container and having means on its lateralouter surface in sealing engagement with the inner surfaces of thecontainer; (d) pressure responsive valve means associated with saidpiston, said valve means being normally closed when there is a minimumof pressure differential on different portion of the valve means andwhich automatically opens in response to a substantial pressuredifferential so that when said container is subjected to moderatecentrifugal force the blood separates into its light phase and heavyphase but the piston stays in the upper portion of the container, andsubsequently when increased centrifugal force is used the valve meansautomatically opens with the light phase passing up through the valvemeans enabling the piston to move down through the light phase whileretaining sealing engagement with the inner surface of the container;(e) a throat within said piston leading from the lower surface thereofto the orifices of said valve means and having walls which areinterrupted with a series of ridges and through which the said lightphase must pass to reach said valve means; and (f) mechanical stop meanson the container whereby the piston when moving through the light phasewill stop a predetermined distance from one of the ends of the containerfollowed by termination of the differential pressure which permits thevalve means to automatically shift from an open position to a closedposition to provide an impervious barrier between the separated lightphase and heavy phase of the blood.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional sideelevational view of a separator assembly of the invention illustrating acannula penetrating one of the closures through which blood isintroduced into the container prior to separatlon.

FIG. 2 is a view similar to FIG. 1 illustrating the sepa ration of theblood into the light phase and heavy phase with the improved pistonengaging the stop means.

DETAILED DESCRIPTION OF THE INVENTION For a better understanding of theinvention, a description of the drawings of the illustrative embodimentsis had, particularly with respect to the embodiments shown in FIGS. 1through 2.

Referring to FIG. 1, it is seen that the separator assembly 10 comprisesa tubular member or container 12 having mounted in each open end 11, 15closures l4 and 16. Closures l4 and 16 are made of a self-sealingelastomeric material, such as rubber, which are capable of receivingcannula 18 penetrated therethrough as illustrated in FIG. 1, forconducting blood into the container. When the cannula is removed theclosure is resealed with no loss of blood passing through thepenetration portion as illustrated in FIG. 2.

Closure 14 is formed having a depending cylindrical body portion and aflanged head portion 22 integrally formed therewith. Body portion 20 hasa diameter slightly greater than the internal diameter of the container12 so that closure 14 when mounted into end 11 provides a pressure fitto seal the end. Head portion 22 is shaped in the form of a hexagon andis slightly greater in diameter than body portion 20 which permits theassembly to be positioned on its side without danger of rolling.

Stopper 16 is formed preferably of the same material as stopper l4.Stopper 16 has a cylindrical body portion 28 and an integrally formedhead portion 30 having an axial recess 24. Body portion 28 has anannular recess 29 to provide a self-sealing penetrable zone 31 tofacilitate insertion of cannula 18 with minimum force while maintaininga sealed closure. As noted above, stoppers l4 and 16 are insertedrespectively into ends 11 and 15, in compression, to maintain ends 11and 15 of container 12 in sealed engagement.

Tubular member or container 12 is formed preferably of glass but asuitable plastic material may be employed. Intermediate ends 11 and 15of tubular member 12 is an annular groove 32 which forms a stop means 34as a part of the inner surfaces of container 12. Piston 40 is heavierthan the light phase of the blood and moves downwardly through the bloodduring high speed centrifugation. Thus, as piston 40 moves from theinitial starting position, illustrated in FIG. 1, to the terminalposition after the separation of the light phase from the heavy phase,as shown in FIG. 2, the piston comes to rest at the stop means 34 formedby annular groove 32 of container 12. The seal of the piston, withrespect to the inner surface of the container, is maintained throughoutits travel-from its initial position of FIG. 1 to its terminal positionof FIG. 2.

Piston 40 includes a tubular metal insert 52 which is mounted in annularrecess 54 of piston 40. Metal insert 52 is preferably made of stainlesssteel or other rigid, chemically inert material having a specificgravity greater than blood. Piston 40 is formed of elastomeric materialand is provided with annular recess 54 which is dimensioned to receivetubular member 52 in interference fit sothat no air space remains inannular recess 54.

The elastomeric portion of piston 40 comprises an outer wall 48 andspaced therefrom is inner wall 46 which defines annular recess 54.Formed integrally with wall 48 are a plurality of axially spaced sealingrings 50 which contact the inner wall surfaces 13 of container 12 insealing engagement. Piston 40 when mounted in container 12 will maintainsealing contact with inner surface 13 of container 12 throughout itspath of travel within container 12. During the centrifuging operationpiston 40 descends and this produces a pressure differential on theopposite sides of the diaphragm portion 44 of piston 40. Diaphragm 44has a relatively small thickness and lies adjacent stopper 14 in itsinitial position as seen in FIG. 1. Diaphragm 44 is made of a resilientmaterial and is provided with a plurality of apertures 42 extendingtherethrough. Diaphragm portion 44 of piston 40 normally closes throat80 within piston 40 which leads from the lower surface 82 of piston 40to apertures 42. As the assembly is being subjected to increasedcentrifugal force causing the piston to descend, the light phase, whichis separated from the heavy phase of the blood, will pass into throatand be guided to apertures 42. Also, since the centrifugal force actingon piston 40 will start to move the piston downwardly, the diaphragm 44will stretch into a dome shape which will open resilient apertures 42.This will enable light phase liquid to flow up through apertures 42 andpermit piston 40 to move from its initial position of FIG. 1 to itsfinal position of FIG. 2 while maintaining sealing engagement with theinner wall 13 of container 12. When piston 40 stops its movement incontainer 12 and comes to rest on stop means 34, the pressuredifferential on each side of diaphragm 44 becomes substantiallyequalized and valve means 42 automatically shifts from the open positionto the closed position even though the assembly is still being subjectedto centrifugal forces.

As seen in FIG. 1, the inner surface 86 of wall 46 defining throat 80 isserrated to provide ridges 88. This series of ridges 88 provide a roughthroat wall 86 which creates pockets or regions of relatively low fluidvelocity in the flow of light phase blood component through the throat80. Particulate matter entrained in the flow of light phase material isdeposited in the crevices behind the ridges 88 as a result of lowervelocity, thereby preventing it from being carried through the apertures42 and into the upper chamber of assembly 10.

Piston 40 as noted above includes tubular insert 52 which is mounted inannular recess 54 by an interference fit with no air space therearound.When piston 40 is subjected to centrifugal forces the radial outwardthrust of hydrostatic force acting on wall 46 is transferred to tubularinsert 52 which resists this thrust and will not transmit it to thesealing rings 50 which would cause increase of friction between piston40 and wall 13 of container 12. Such increase of friction could stallthe piston and prevent it from descending. Therefor, this excessfriction must be eliminated, which is accomplished as described.

As illustrated in FIG. 2, piston 40 has completed its travel withincontainer 12 and is stopped from further movement in container 12 bystop means 34 and valve means 42 are closed. Also, a portion of thelight phase remains above the separated heavy phase and is not utilizedas part of the separated light phases.

When operating the separator assembly of the invention herein it ispreferred that the assembly be evacuated so that when cannula l8penetrates closure 16 blood will automatically fill container 12. It isalso contemplated to provide a separator assembly suitable for use withthe blood collecting assembly disclosed in US. Pat. Nos. 2,460,641;3,469,572; 3,494,352 and 3,779,383. It is important when fillingassembly 10 that blood be introduced into container 12 through stopper16 to obviate the possibility of having blood cells trapped on the topof piston 40 which later will form part of the chamber where the lightphase will be collected and would contaminate the light phase with redcells and/or clotted material.

After cannula 18 is withdrawn and container 12 is filled with blood theassembly is placed in a centrifuge and is separated employing moderatecentrifugal force which does not cause the piston to move from itsinitial position. Thereafter the rotational speed of the centrifuge isincreased which causes the piston to slide downwardly thereby producinga substantial differential pressure on the diaphragm. The valve means 42automatically opens and the piston moves downwardly through the lightphase with the light phase passing through the throat and valve means.Piston 40 maintains sealing engagement with the inner wall 13 ofcontainer 12. The piston completes its movement when it engages stopmeans 34 and terminates the pressure differential, automatically closingthe valve means while the assembly is subjected to centrifugal forces.Thus, diaphragm 44 comprises an impervious barrier between the lightphase of blood and the heavy phase of blood when piston 40 is in theposition illustrated in FIG. 2. Then centrifugal forces are terminatedand the separated blood components are ready for use What is claimed is:

1. A self-contained fluid separator assembly capable of separating bloodinto its component parts of plasma or serum and cellular portioncomprising:

a. a container having at least one open end which is adapted to receiveblood for subsequent separation into a light phase and a heavy phase;

. a closure sealing the open end of the container, the

closure being formed of a self-sealing elastomeric material which ispenetrable by a cannula through which blood to be separated is conductedinto the container;

0. a piston having a specific gravity relatively greater than thecellular portion of the blood and slidably mounted in the upper portionof the container and having means on its lateral outer surface insealing engagement with the inner surfaces of the container;

(1. pressure responsive valve means associated with said piston, saidvalve means being normally closed when there is a pressure differentialon different portions of the valve means below a predetermined value andwhich automatically opens in response to a pressure differential whichis greater than said value so that when said container is subjected tomoderate centrifugal force the blood separates into its light phase andheavy phase but the piston stays in the upper portion of the container,and subsequently when increased centrifugal force is used the valvemeans automatically opens with the light phase passing up through thevalve means enabling the piston to move down through the light phasewhile retaining sealing engagement with the inner surfaces of thecontainer;

e. a throat within said piston leading from the lower surface thereof tosaid valve means, said throat having walls which are serrated with aseries of ridges for trapping unwanted cellular material; and

. mechanical stop means on the container whereby the piston when movingthrough the light phase will stop a predetermined distance from oneofthe ends of the container followed by termination of the differentialpressure which permits the valve means to automatically shift from anopen position to a closed position to provide an impervious barrierbetween the separated light phase and heavy phase of the blood.

2. The self-contained fluid separator of claim 1 wherein said containercomprises a tubular body open at each end in which closures formed ofelastomeric material are mounted in sealing engagement with the tubularbody and a piston disposed adjacent one of said closures.

3. The self-contained fluid separator of claim 1 wherein the pistonincludes a rigid tubular sleeve mounted in a generally tubular outerbody portion formed of rubber and having a plurality of spaced radialribs on its outer portion for sealing engagement with the inner walls ofthe container and a diaphragm forming a wall across one end of thegenerally tubular rubber sleeve and having apertures formed thereinwhich are normally closed but which automatically open when subjected toa substantial pressure differential on each side of the diaphragm.

4. The piston of claim 1 wherein a tubular metal sleeve is mounted insealing engagement in a complementary annular recess formed in a rubberbody portion having an interference fit so that substantially no airspace is provided between the walls defining the an nular recess and theinner and outer walls of the rigid tubular member.

5. The self-contained fluid separator of claim 1 wherein the stop meansformed on the container is an annular groove interposed between the endsof the container forming an annular rim on the inner surfaces of thecontainer so that said piston is prevented from passing the stop meanswhen subjected to centrifugal forces.

1. A self-contained fluid separator assembly capable of separating bloodinto its component parts of plasma or serum and cellular portioncomprising: a. a container having at least one open end which is adaptedto receive blood for subsequent separation into a light phase and aheavy phase; b. a closure sealing the open end of the container, theclosure being formed of a self-sealing elastomeric material which ispenetrable by a cannula through which blood to be separated is conductedinto the container; c. a piston having a specific gravity relativelygreater than the cellular portion of the blood and slidably mounted inthe upper portion of the container and having means on its lateral outersurface in sealing engagement with the inner surfaces of the container;d. pressure responsive valve means associated with said piston, saidvalve means being normally closed when there is a pressure differentialon different portions of the valve means below a predetermined value andwhich automatically opens in response to a pressure differential whichis greater than said value so that when said container is subjected tomoderate centrifugal force the blood separates into its light phase andheavy phase but the piston stays in the upper portion of the container,and subsequently when increased centrifugal force is used the valvemeans automatically opens with the light phase passing up through thevalve means enabling the piston to move down through the light phasewhile retaining sealing engagement with the inner surfaces of thecontainer; e. a throat within said piston leading from the lower surfacethereof to said valve means, said throat having walls which are serratedwith a series of ridges for trapping unwanted cellular material; and f.mechanical stop means on the container whereby the piston when movingthrough the light phase will stop a predetermined distance from one ofthe ends of the container followed by termination of the differentialpressure which permits the valve means to automatically shift from anopen position to a closed position to provide an impervious barrierbetween the separated light phase and heavy phase of the blood.
 2. Theself-contained fluid separator of claim 1 wherein said containercomprises a tubular body open at each end in which closures formed ofelastomeric material are mounted in sealing engagement with the tubularbody and a piston disposed adjacent one of said closures.
 3. Theself-contained fluid separator of claim 1 wherein the piston includes arigid tubular sleeve mounted in a generally tubular outer body portionformed of rubber and having a plurality of spaced radial ribs on itsouter portion for sealing engagement with the inner walls of thecontainer and a diaphragm forming a wall across one end of the generallytubular rubber sleeve and having apertures formed therein which arenormally closed but which automatically open when subjected to asubstantial pressure differential on each side of the diaphragm.
 4. Thepiston of claim 1 wherein a tubular metal sleeve is mounted in sealingengagement in a complementary annular recess formed in a rubber bodyportion having an interference fit so that substantially no air space isprovided between the walls defining the annular recess and the inner andouter walls of the rigid tubular member.
 5. The self-contained fluidseparator of claim 1 wherein the stop means formed on the container isan annular groove interposed between the ends of the container formingan annular rim on the inner surfaces of the container so that saidpiston is prevented from passing the stop means when subjected tocentrifugal forces.